Facile fabrication of highly catalytic-active Ag2CO3/AgBr/graphene oxide ternary composites towards the photocatalytic wastewater treatment

Ag₂CO₃/AgBr/graphene oxide (Ag₂CO₃/AgBr/GO) ternary composites with different percentages of GO were fabricated by a facile co-precipitation strategy. The composites were characterized in the aspect of phase composition, light absorption performance, and micromorphology etc. The activity of the composites was studied by photocatalytic degradation of colored organic dye (rhodamine B, RhB) and colorless organics (phenol) under the shine of visible light. The optimized Ag₂CO₃/AgBr/GO-7.5 composites revealed the most excellent photocatalytic activity, which exhibited an apparent reaction rate constant exceeding that of pristine AgBr and Ag₂CO₃ by a factor of 107 and 5.63, respectively. The outstanding performance can be attributed to the effective separation of electrons and holes as well as the strong light absorption ability resulting from the Ag₂CO₃/AgBr/GO heterostructure. Moreover, it was verified that h⁺ and •O₂^- were two major active substances responsible for the decomposition of organic pollutants according to the free radical-trapping experiments. Besides, a probable reaction mechanism referring to the charge transfer and separation in the composites was proposed and discussed in detail.

Ag2CO3-halloysite nanotubes composite with enhanced removal efficiency for water soluble dyes

The release of water soluble dyes into the environment is an utmost concern in many countries. This paper presents the effects of Ag₂CO₃-halloysite composites on the efficient removal of water soluble dyes. In this study, NaHCO₃ solution was added dropwisely to halloysite nanotubes (HNTs) dispersed in aqueous AgNO₃ to form Ag₂CO₃-HNTs composite. The synthesized Ag₂CO₃-HNTs composite was characterized with Diffused Reflectance Spectroscopy (DRS), X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX) and Fourier Transform Infra-Red (FT-IR) spectroscopy. The photocatalytic activity and the adsorption capacity of Ag₂CO₃-HNTs on methylene blue and rhodamine b dyes were dependent on pH and the amount of HNTs used in the synthesis. The photodegradation efficiency of Ag₂CO₃ was lower when compared with that of the composite material. This observation is due to the reduction in the electron-hole recombination with the HNTs acting as electron trapping site and the enhanced aqueous dispersity of Ag₂CO₃-HNTs. The enhanced adsorption of water soluble dyes by the Ag₂CO₃-HNTs resulted from the electrostatic attraction of cationic dyes to the surface of the HNTs (negatively charged). The Ag₂CO₃-HNTs therefore removed dye pollutants through a combination of photocatalytic and adsorption processes. The results obtained during the study confirmed the potential application of Ag₂CO₃-HNTs composite in water treatment technologies.